The present invention relates to fabrication of finely featured electronic, chemical, and mechanical devices.
Electronic and electromechanical components are presently fabricated in large, immobile manufacturing facilities that are tremendously expensive to build and operate. For example, semiconductor device fabrication generally requires specialized microlithography and chemical etching equipment, as well as extensive measures to avoid process contamination. The total amount of time required for processing of a single chip may be measured in days, and typically requires repeated transfer of the chip into and out of vacuum conditions.
In addition to their expense, the fabrication processes ordinarily employed to create electronic and electromechanical components involve harsh conditions such as high temperatures and/or caustic chemicals, limiting the ability to integrate their manufacture with that of functionally related but environmentally sensitive elements. For example, the high temperatures used in silicon processing may prevent three-dimensional fabrication and large-area fabrication; these temperatures are also incompatible with heat-sensitive materials such as organic and biological molecules. High temperatures also preclude fabrication on substrates such as conventional flexible plastics, which offer widespread availability and low cost.
Despite intensive effort to develop alternatives to these processes, no truly feasible techniques have yet emerged. U.S. Pat. No. 5,817,550, for example, describes a low-temperature roll-to-roll process for creating thin-film transistors on plastic substrates. This approach faces numerous technical hurdles, and does not substantially reduce the large cost and complexity associated with conventional photolithography and etching processes.
U.S. Pat. No. 5,772,905 describes a process called xe2x80x9cnanoimprint lithographyxe2x80x9d that utilizes a silicon mold, which is pressed under high pressure and temperature into a thin film of material. Following cooling with the mold in place, the material accurately retains the features of the mold. The thin film may then be treated to remove the small amount of material remaining in the embossed areas. Thus patterned, the film may be used as a mask for selectively etching underlying layers of functional materials. This process is capable of producing patterns with very fine resolutions at costs significantly below those associated with conventional processes. But it is quite complicated, requiring numerous time-consuming steps to create a single layer of patterned functional material. The technique requires high application pressures and temperatures at very low ambient pressures, thereby imposing significant complexity with attendant restriction on the types of materials that can be patterned. Perhaps most importantly, this technique is limited to producing single-layer features, thereby significantly limiting its applicability to device fabrication.
U.S. Pat. No. 5,900,160 describes the use of an elastomeric stamp to mold functional materials. In particular, the stamp is deformed so as to print a self-assembled molecular monolayer on a surface. This process, also called MIMIC (Micromolding Against Elastomeric Masters), is significantly simpler than nanoimprint lithography, and can be performed at ambient temperatures and pressures. But the technique is generally limited to low-resolution features (in excess of 10 xcexcm), and more importantly, the types of geometries amenable to molding by this technique are limited.
It is, accordingly, an object of the present invention to provide an easily practiced, low-cost process for directly patterning functional materials without the need for multi-stage etching procedures.
Another object of the invention is to increase the speed with which layers of functional materials can be patterned.
Still another object of the invention is to provide a fabrication process that requires no unusual temperature, pressure, or ambient conditions, thereby increasing the range of materials amenable to patterning.
A further object of the invention is to facilitate convenient nanoscale patterning of multiple adjacent layers.
Yet another object of the invention is to planarize deposited materials as part of the application process, eliminating the need for additional planarizing processes (such as chemical mechanical polishing), thereby facilitating fabrication of complex three-dimensional devices employing many (e.g., in excess of 100) layers.
To achieve the foregoing and other objects, the present invention utilizes an elastomeric stamp to facilitate direct patterning of electrical, biological, chemical, and mechanical materials. In accordance with the invention, a thin film of material is deposited on a substrate. The deposited material, either originally present as a liquid or subsequently liquefied, is patterned by embossing at low pressure using an elastomeric stamp having a raised pattern. The patterned liquid is then cured to form a functional layer. The deposition, embossing, and curing steps may be repeated numerous times with the same or different liquids, and in two or three dimensions. The various deposited layers may, for example, have varying electrical characteristics, interacting so as to produce an integrated electronic component.